Systems and methods for testing a semiconductor memory device having a reference memory array

ABSTRACT

Semiconductor memory testing devices and methods are disclosed. In one respect, a device is disclosed that includes a first memory cell array having a first bit-line and a plurality of first memory cells coupled to the first bit-line; a second memory cell array having a second bit-line and a plurality of second memory cells coupled to the second bit-line, the number of second memory cells being smaller than that of the first memory cells; a sense amplifier coupled to the first bit-line and a first end of the second bit-line; a word decoder configured to operate the second memory cells responsive to a first test signal; and a transistor coupled to a second end of the second bit-line and operated by a second test signal.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. application Ser. No.15/130,789 filed on Apr. 15, 2016. This application is incorporated byreference herein in its entirety and for all purposes.

TECHNICAL FIELD

Semiconductor memory testing devices and methods are disclosed.

BACKGROUND

Memory devices that employ an open bit-line architecture can make use ofsmaller memory cell sizes when compared to that of folded bit-linearchitectures. In some current examples, an open bit-line architecturemay use a 6F2-cell, whereas a 8F2-cell is typically used in a foldedbit-fine architecture. Drawbacks of the open bit-line architectureinclude large area penalties in the edge sections, which sections havehalf of the bit-lines tied to, reference voltage (˜Vary/2) as a dummyarea for sensing noise immunity. Also, bit-line lengths generally tendto be extended to lengths such as 832-bit or 1 K-bit because die sizereduction is desirable with improvements in area efficiency and Cd/Csratios. However, extended bit-line may have enlarged edge sections,which limits die size reduction because of the accompanying dummy areaincrease. Operational voltage tends to become lower while, at the sametime, process evolution has developed decreased bit-line capacitance andsmaller Cd/Cs ratio. In open bit-line scheme, an extended bit-line isnot always compatible with smaller die sizes. Typically, there is anoptimal bit line length for a given die size. Additionally, undernanofabrication, a memory device's operational voltage tends to be lowerdue to consideration of transistor reliability. In some instances, senseamplifier imbalances tend not to be improved due to somewhat increasedprocess variation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-C are schematic illustrations of an example memory device inaccordance with the present disclosure.

FIG. 2 is a schematic illustration of a sense amplifier in accordancewith the present disclosure.

FIGS. 3A-B are schematic illustrations of various example arrangementsfor storage and reference arrays in accordance with the presentdisclosure.

FIG. 4 is a schematic illustration of a memory device embodiment thatshows the activation of certain word-lines in accordance with thepresent disclosure.

FIG. 5 is a schematic illustration of a memory device embodiment thatshows the use of dummy word-lines to improve sense amplifier balanceduring the pre-charge phase in accordance with the present disclosure.

FIGS. 6A-B are signal trace diagrams that compare the behavior of amemory circuit embodiment with and without the use of a dummy word-line.

FIG. 7 is a schematic illustration of a memory device embodiment thatincludes the use of dummy word-lines in adjacent storage arrays toimprove the sense amplifier balance during the pre-charge phase inaccordance with the present disclosure.

FIGS. 8A-B are signal trace diagrams that compare the behavior of anmemory circuit embodiment with and without the use of a dummy word-line.

FIG. 9 is a flow chart that illustrates a test flow in accordance withpresent embodiments.

FIG. 10 is a schematic illustration of a tester embodiment for a memorydevice in accordance with the present disclosure.

FIG. 11A is a flow chart that illustrates a test-mode that executes acheck of equalization levels in accordance with a first embodiment

FIG. 11B is a timing diagram that shows various signal traces thatillustrate an equalization level check for a memory device in accordancewith the present disclosure.

FIG. 12 is a schematic illustration of a tester embodiment for a memorydevice in accordance with the present disclosure.

FIG. 13A is a flow chart that illustrates a test-mode that executes acheck of equalization levels in accordance with a second embodiment.

FIG. 13B is an additional timing diagram that shows various signaltraces that illustrate an equalization level check for a memory devicein accordance with the present disclosure.

FIG. 14 is a schematic illustration a tester embodiment for a memorydevice in accordance with the present disclosure.

FIG. 15A is a flow chart that illustrates a test-mode that executes asense amplifier offset check in accordance with an embodiment.

FIG. 15B is a timing diagram that shows various signal traces thatillustrate the sense amplifier offset checking for a memory device inaccordance with the present disclosure.

FIGS.16A-B are diagrams for example sense amplifier controllers inaccordance with the present disclosure.

FIGS. 17A-B are diagrams for example LIO-EQ circuits in accordance withthe present disclosure.

FIGS. 18A-B are diagrams for example RWAMP circuits in accordance withthe present disclosure.

DETAILED DESCRIPTION

The present disclosure is directed to semiconductor memory testingdevices and methods. A semiconductor memory in accordance with thisdisclosure may include a memory array section that functions as areference section, rather than a data storage section. Specifically, thereference section functions to support a balanced operation of the senseamplifiers associated with memory device and does not generally storedata. The reference memory array is generally smaller than othersections used for data storage. When the memory device enablesword-lines in a storage array adjacent to the reference array, thereference array balances the capacitance of storage array bit linesthrough a group of activated word-lines in the reference array. Presentembodiments are directed to testing methods that determine whichword-lines to be included and which are not to be included in theactivated word-line group of the reference array. Additional embodimentsare directed to further improvements that use dummy words lines inconnection with memory access operations and pre-charge operations.

System Overview

FIGS. 1A-C illustrates an example memory device 100 in accordance withthe present disclosure. A memory device 100 may include an of a numberof suitable memory devices, such as a Dynamic Random Access Memory(DRAM) device. FIG. 1A is a schematic of the example memory device 100that illustrates a number of memory banks, as well as various controlcircuits associated with the memory banks. FIG. 1B is an additionalschematic of the example memory device 100 that includes a number ofmemory arrays within a particular memory bank. FIG. 1C is an additionalschematic of the example memory device 100 that shows individual memorycells within a number of memory arrays.

Generally, a memory device 100 in accordance with the present disclosuremay include hundreds of separate memory arrays. FIG. 1A shows a numberof memory banks 102, which include a number of memory arrays. FIGS. 1B-Cshow at least two memory arrays 104, 108 by way of example and notlimitation. The memory banks 102 (and thus the memory arrays 104, 108)are associated with an address input circuit 112, an address decoder113, a word, decoder 116 (also referred to as a row decoder), a bitdecoder 120 (also referred to as a column decoder), and with a pluralityof shared sense amplifiers 124. FIGS. 1B-C also shows sense amplifiercontroller 126, which are described in greater detail below inconnection with FIGS. 16A-B. The memory device 100 of FIG. 1C includes afirst memory array arranged as a storage array 104 and a second memoryarray arranged as a reference array 108. A storage array 104 isgenerally configured to store data that is accessed through theoperation of the address input circuit 112, word decoder 116, and bitdecoder 120. As described in, greater detail below, the reference array108 is generally not configured to store data, but rather is configuredto be selectively activated to support a balanced operation of the senseamplifiers 124, FIG. 1C also shows LIO-EQ circuits 127, which aredescribed in greater detail below in connection with FIGS. 17A-B.

Each memory array 104, 108 includes a plurality of memory cells 128coupled to a plurality of intersecting word lines 132 and bit-lines 136.Each memory cell 128 is associated with one of the word-lines 132 andwith one of the bit-lines 136. Thus, each memory cell 128 has an address140 that uniquely identifies its location in the memory device 100 basedOn the intersection of the word-line 132 and the bit-line 136 associatedwith the particular memory cell 128. Each memory cell 128 is generallyconfigured to store a bit of data that is readable and writable throughthe operation memory device 100. In addition, the memory arrays 104, 108may include a plurality of dummy cells coupled to a dummy word-line andto the bit-lines 136. Each dummy cell is uniquely identified by theintersection of the dummy word-line and a bit-line 136. The dummy cellsare generally not configured to store data, but rather to be addressedto add capacitance to a bit-line 136 so as to balance the load seen bythe sense amplifiers 124. These and other aspects of memory cells anddummy cells in accordance with the present disclosure are described ingreater detail below, FIGS. 1A-C shows a number of word-lines and bitlines by way of example and not limitation. An exemplary memory device100 may comprise hundreds of word-lines and hundreds of bit-lines andany given number of dummy word-lines.

FIG. 1A includes illustrations of example memory cells 128. The memorycells of the various memory arrays and/or dummy cells (described ingreater detail below) may have the same configuration as the examplememory cells 128 shown in FIG. 1A. The example memory cell 128 includesa storage device capable of holding a charge, such as a capacitor 160,and an access transistor 164 configured as a switch. The example memorycell 128 may hold a single bit of data through the presence or absenceof a charge on the capacitor 160. When arranged as part of a dummy cell,the capacitor 160 may be set to a predetermined state, such as adischarged state. The access transistor 164 has a respective gatecoupled to a word-line 132 associated, with the memory cell 128. Whenthe access transistor 164 is activated, the capacitor 160 in the memorycell 128 becomes electrically coupled to the bit-line 136 associatedwith the memory cell 128. The charge on the capacitor 160, if any, maythen pass to the bit-line 136 to be read through the operation of asense amplifier 124.

The sense amplifiers 124 may be generally configured with two sides,each of which is coupled to a particular segment of a bit-line 136. Thememory arrays 104, 108 illustrated in FIGS. 1A-C are implemented usingan “open” bit-line Configuration. That is, for each sense amplifier 124,one of the bit-line segments coupled to the sense amplifier 124 islocated within the first memory array 104, while the other bit-linesegment coupled to the sense amplifier 124 is located within the secondmemory array 108. The memory arrays 104, 108 may also be implementedusing a variety of alternative configurations, such as “folded” bit-lineconfiguration, in which both bit-lines segments coupled to each senseamplifier are located within the same memory array. In one embodiment,the word-lines 132, the dummy word-lines, and the bit-lines 136 arelubricated as metal lines on an integrated circuit.

A sense amplifier 124 may be generally configured to sense the contentof a memory cell 128 by amplifying and outputting a voltage differencethat is present on a pair of bit-lines segments to which the senseamplifier 124 is coupled. Here, the sense amplifier 124 may be coupledto two bit-lines segments that are associated with adjacent memoryarrays. By way of example, FIGS. 1B-C shows sense amplifiers 124 thatare coupled to a first bit-line segment 168 associated with the firstmemory array 104. The sense amplifiers 124 are additionally coupled to asecond bit-line segment 172 associated with the second memory array 108.During a read operation or other memory access operation for a desiredmemory cell 128, a sense amplifiers 124 may detect the presence orabsence of a charge on the capacitor 160 in the desired memory cell 128by comparing the voltage on the two bit-line segments 168, 172 coupledto the sense amplifier 124.

To detect the state of the capacitor 160 in a particular memory cell128, the Memory cell 128 is selected, or addressed. The address 140 forthe desired memory cell 128 is provided to the address input circuit112, which through the address decoder 113 provides signals representingthe address 140 to the word decoder 116 and to the bit decoder 120. Whena particular memory cell 128 is addressed, the word decoder 116 and thebit decoder 120 pre-charge a first bit-line segment 168 to which thememory cell 128 is coupled to a predetermined voltage level, referred toas Vary/2. This bit-line segment 168 is coupled to a sense amplifier 124that, in turn, is coupled to a second bit-line segment 172 in anadjacent memory array. This second bit-line segment 168 is additionallypre-charged by the word decoder 116 and the bit decoder 120 as part ofaccessing the memory cell 128. Once the bit-line segments 168, 172 arepre-charged, the bit decoder 120 applies a predetermined voltage to theword-line 132 coupled to the memory cell 128 a, which activates theaccess transistors 164 in each of the memory cells 128 coupled to theselected word-line 132.

When the access transistor 164 in the addressed memory cell 128 isactivated, the capacitor 160 in the memory cell 128 becomes electricallycoupled to the first bit-line segment 168. If the capacitor 160 in theaddressed memory cell 128 is charged when the access transistor 164 isactivated, then the capacitor 160 discharges onto the first bit-linesegment 168, and the voltage on the first bit-line segment 168 changesfrom Vary/2. On the other hand, if the capacitor 160 in the addressedmemory cell 128 is not charged when the access transistor 164 isactivated, then the voltage on the first bit-line segment 168 remains atVary/2. As mentioned, the first bit-line segment 168 is coupled to asense amplifier 124 that, in turn, is coupled to a second bit-linesegment 172 in an adjacent memory may. The memory cells coupled to thesecond bit-line segment 172 are not accessed when the addressed memorycell 128 is accessed. Here, the second bit-line segment 172 remains atthe pre-charge voltage level Vary/2. Thus, the state of the capacitor160 in the desired memory cell 128 can be detected by comparing thevoltage on the first bit-line segment 168 with the measured voltage onthe second bit-line segment 172.

For example, if the capacitor 160 in the memory cell 128 is charged,then the voltage on the first bit-line segment 168 will change fromVary/2 when the access transistor 164 in the cell 128 is activated.Thus, a voltage differential will exist when the voltage on the firstbit-line segment 168 and the voltage on the second bit-line 172 arecompared. On the other hand, if the capacitor 160 in the, memory cell128 is not charged, then the voltage on the first bit-line segment 168will remain at Vary/2 when the access transistor 164 in the memory cell128 is activated. Thus, no voltage differential will exist when thevoltage on the first bit-line segment 168 and the voltage on the secondbit-line 172 are compared. Accordingly, the state of the capacitor 160in the memory cell 128 can be determined by detecting the presence orthe absence of a voltage differential between the first bit-line segment172 and the second bit-line segment 168.

FIG. 2 illustrates a sense amplifier 200 embodiment. The sense amplifier200 is coupled to a pair of bit-lines, referred to as a first bit-line204 a and a second bit-line 204 b. In one example, the sense amplifiers124 illustrated in FIG. 1 may be implemented using the sense amplifier200 Shown in FIG. 2. In this regard, the first bit-line 204 a may,correspond to the first bit-line segment 168, and the second bit-line204 b may correspond to the second bit segment 172. Referring to FIG. 2,the sense amplifier 200 may receive a power supply voltage, Vary, via apower supply line 208. The sense amplifier 200 may be connected to a lowvoltage such as ground through a VSS connection line 212. The senseamplifier 200 additionally receive an equalization voltage VBLP, via anequalization voltage line 216. The sense amplifier 200 may include afirst group of transistors 220 that are connected to the bit-lines 204a-b and to the equalization voltage line 216. The sense amplifier 200may additionally include a second group of transistors 224 that areconnected to the bit-lines 204 a-b and to the power supply 208 andground 212 connections.

The first group of transistors 220 are generally configured topre-charge the bit-lines 204 a-b in preparation for a read operation orother memory access operation. In the first group of transistors 220,the first bit-line 204 a is coupled to the drain a first n-channeldevice 228 a and to the drain of a second n-channel device 228 b. Thesecond bit-line 204 b is coupled to the source of a third n-channeldevice 228 c and to the source of the second n-channel device 228 b. Thesource of both the first n-channel device 228 a and the source of thethird n-channel 228 c are coupled to the equalization voltage line 216.The gates of the first n-channel device 228 a, the second n-channeldevice 228 b, and the third n-channel device 228 c are each coupled toan equalization control line 232.

The second group of transistors 224 may be generally configured to sensea voltage difference between the bit-lines 204 a-b. In the second groupof transistors 220, the first bit-line 204 a is coupled to the gate of afirst n-channel device 236 a and to the gate of a first p-channel device240 a. Similarly, the second bit-line 204 b is coupled to the gate of asecond n-channel device 236 b and to the gate of a second p-channeldevice 240 b. In addition, the first bit-line 204 a is coupled to thedrain of the second n-channel device 236 b and to the drain of thesecond p-Channel device 240 b. Likewise, the second bit-line 204 b iscoupled to the drain of the first n-channel device 236 a and to thedrain of the first p-channel device 240 a. The sources of the twon-channel devices 236 a, 236 b are both coupled to ground. The sourcesof the two p-channel devices 240 a, 240 b are both coupled to the powersupply line 208.

When the sense amplifier 200 is sensing the state of a memory cell, thebit-lines 204 a, 204 b are pre-charged to a predetermined voltage,Vary/2, through, the operation of the first group of transistors 220.Word-lines are then asserted so as to couple memory cells to thebit-lines 204 a, 204 b) in preparation for amplification by the secondgroup of transistors 220. If the sense amplifier 200 is sensing thestate of a memory cell that is coupled to the first bit-line 204 a andthat has a charged capacitor, then the capacitor discharges onto thefirst bit-line 204 a when the memory cell is addressed. The discharge ofthe capacitor onto the first bit-line 204 a causes a slight increase involtage on the first bit-line 204 a. On the other hand, if the capacitorin the addressed memory cell is not charged, then the voltage on thefirst bit-line 204 a remains at Vary/2. The sense amplifier 200 sensesthe slight increase in voltage on the first bit-line 204 a for absencethereof) by comparing the voltage on the lint bit-line 204 a with thevoltage on the second bit-line 204 b. Thus, the sense amplifier 200senses the state of the capacitor in the desired memory cell. The senseamplifier 200 is configured to detect a slight voltage differentialexisting between two input voltage signals received via the bit-lines204 a, 204 b. Furthermore, the sense amplifier 200 is configured toamplify the slight voltage differential to a value of about Vary and toprovide two output voltage signals via the bit-lines 204 a, 204 b havingthe amplified voltage differential.

As an example, if the sense amplifier 200 is sensing the state of amemory cell that is coupled to the first bit-line 204 a and that has acharged capacitor, then the discharge of the capacitor onto the firstbit-line 204 a causes a slight increase in voltage on the first bit-line204 a. A typical value for the slight increase in voltage on the firstbit-line 204 a caused by the discharge of the capacitor is about 50 mV.The sense amplifier is configured to detect the voltage differential ofabout 50 mV existing between the first bit-line 204 a and the secondbit-line 204 b. If the value of Vary/2 is about 1.8 V, then the senseamplifier 200 amplifies the 50 mV voltage differential to a voltagedifferential of about 1.8 V. The sense amplifier 200 provides two outputvoltage signals via the bit-lines 204 a, 204 b with a voltagedifferential of about 1.8 V existing between them.

The bit-lines 204 a-b associated with the sense amplifier 200 mayinclude a global portion (MIO) and a local portion (LIO). For example,the first bit-line 204 a may include a global bit-line 244 a thatconnections the sense amplifier 200 to the data readout circuits thatare coupled to or otherwise associated with the memory device of whichthe sense amplifier 200 is a component. The first bit-line 204 a mayalso include one or more local bit-lines 248 a that are coupled to theglobal bit-line 244 a through an access transistor 252 a. The localbit-line 248 a provides access to an individual memory cell of thememory device. Data is write in and read out of the memory device bybeing written across the global bit-line 244 a and into and out of anindividual memory cell through the access transistor 252 a and othercomponents of the memory device. The first global bit-line 244 a, thefirst local bit 248 a and the first access transistor 252 a shown inFIG. 2 may be associated with a first memory array adjacent to the senseamplifier 200. FIG. 2 additionally shows a second global bit-line 244 b,a second local bit 248 b and a second access transistor 252 a that maybe associated with a second memory array adjacent to the sense amplifier200.

Reference Arrays

A memory device in accordance with the present disclosure may includeone or more reference arrays that are generally not configured to storedata, but rather configured to be selectively activated to support abalanced operation of sense amplifiers associated the memory device. Thereference array may replace conventional edge arrays that are larger andthat include memory cells used for data storage. Typically, half of thememory cells in a conventional edge array are used to store data andthus are connected to sense amplifiers that are disposed between theedge array and an adjacent memory array. The remaining half of thememory cells in a conventional edge array are typically unused and maybe tied high by being coupled to a power supply voltage. In aconventional arrangement, the edge array is typically the same site asother arrays in the memory device. Thus, the bit-line segments in theedge array are typically the same size as the bit-line segment in thearray adjacent to the edge array. A conventional edge array may eitherbe the activated side or the reference side in a read operation or othermemory access operation. In either case, the capacitance on either sideof the sense amplifier typically balance because the bit-line segmentsare the same length,

In contrast to a conventional edge array, an edge array in accordancewith the present disclosure may be smaller and may only be used as areference side in a read operation or other memory access operation.More specifically, as shown in FIG. 1, a storage array 104 may contain agreater number of word-lines 132 and thus may be generally wider thanthe reference array 108. By way of illustration, FIG. 1 shows a fractionof the number of words lines 132 that may be included in a storage array104. Generally, a storage array 104 in accordance with the presentdisclosure may include hundreds or thousands of word-lines 132. Incontrast, reference array 108 in accordance with the present disclosuremay include a smaller number of word-lines 132. In some embodiments, areference array 108 may include as few as three or four word-lines 132.In other embodiments, a reference array 108 may include between threeand fifty word-lines 132. FIGS. 3A-B show various example arrangementsfor the storage 304 and reference arrays 308 in accordance with thepresent disclosure. The storage 304 and references arrays 308 maycorrespond to the storage 104 and reference arrays 108 shown in FIG. 1.As shown in FIG. 3A, a reference array 308 may be arranged at an edge ofa memory device 300. As shown in FIG. 3B, a reference, array 308 may bean edge of a memory bank associated with a memory device 302.

Referring again to FIG. 1, the example memory device 100 shown thereinincludes a reference array 108 provided in association with a storagearray 104. The reference array 108 includes a number of memory cells 128that, may be activated through word-lines 132 to which they are coupled.In accordance with present embodiments, the memory cells 128 of thereference array 108 may not generally be used to store data. Rather, thememory cells 128 in the reference array 108 may be activated in groupsat least during a read operation or other memory access operation inorder to support a balanced operation of the sense amplifiers 124 thatare used to read out data as described above. More specifically, thememory cells 128 in the reference array 108 are activated to addcapacitance to the bit-line segment 172 such that this added capacitanceis seen by the sense amplifier 124 a-bwhen the sense amplifier 124amplifies the voltage difference on the bit-line segments 168, 172. Asused herein, certain word-lines 132 are “always activated” in the sensethat they are always activated when a memory access operation occurs. Inone implementation, the always activated word-lines 132 are associatedwith the activated memory cells 128 in the reference array 108 and areasserted at all times asserted. Alternatively, the always activated,word-lines 132 may be associated with the activated memory cells 128 inthe reference array 108 may be asserted just during the memory accessoperation in order to conserve power.

The number of word-lines 132 in the reference array that are activatedand thus the amount of capacitance added to the second bit-line segment172 may be chosen to balance the capacitance present on the firstbit-line segment 168. The amount of capacitance that may be added tobalance the capacitance present on the first bit-line segment 168 may bedetermined by a number of considerations including signal amounts thatwill typically be available at the sense amplifier 124. In order to morefully describe the process, reference is made to Equation (1), whichgenerally governs the amount of voltage that is available to producesignal at the sense amplifier 124 during a read operation or othermemory operation.

$\begin{matrix}{V_{sig} = {{\frac{V_{ary}}{2} \times \frac{1}{{{Cd}/{Cs}} + 1}} \geqq V_{limit}}} & (1)\end{matrix}$

In Equation (1), Vsig is the voltage available for the operation thesense amplifier; Vary is the power supply voltage, of memory array; Cdis capacitance of the bit-line segment; Cs is the capacitance of amemory cell; and Vlimit the needed signal amount for proper operation ofthe sense amplifier. As can be seen from Equation (1), the amount ofvoltage available for the operation the sense amplifier (Vsig) isinversely related to the ratio of the capacitance of the bit-linesegment (Cd) to the ratio of the, memory cell (Cs). As the Cd/Cs ratio,increases, the amount of voltage available for the operation the senseamplifier decreases. As the Cd/Cs ratio decreases, the amount of voltageavailable for the operation the sense amplifier increases. Thus, theCd/Cs ratio tends to be smaller to keep an amount of the signalavailable for the sense amplifier's sensing operation. In some largernanometer processes, Vary is typically around approximately 2V. Here,the Cd/Cs ratio is around approximately 5. In some smaller nanometerprocesses, Vary can be around approximately 1V. Here, the Cd/Cs ratiocan be less than or around approximately 2. By way of example, Equation(2) sets forth the Cd/Cs ratio for this smaller nanometer process.

Cd/Cs 2 (2)   (2)

As mentioned in connection with FIG. 1, the number of word-lines 132 inthe reference array that are activated and thus the amount ofcapacitance added to the second bit-line segment 172 may be chosen tobalance the capacitance present on the first bit-line segment 168. TheCd/Cs ratio for a given memory device may be used to gauge the amount ofcapacitance that, is present on a first bit-line segment 168. During amemory read or other memory access operation such, as for the examplememory cell 128 a, the amount of capacitance present on the firstbit-line segment 168 includes the capacitance of the first bit-linesegment 168 plus the capacitance of the activated memory cell 128 a.Thus, using the notation introduced above, the capacitance of a bit-linesegment 168 during a memory read operation is given by the quantity(Cd+Cs). Given a known Cd/Cs ratio, this quantity may be manipulated toexpress, the capacitance of a bit-line segment 168 in terms of a numberof memory cell capacitances. Continuing with the smaller nanometerexample above, the capacitance of a bit-line segment 168 as given by thequantity (Cd+Cs) can be expressed as follows:

Cd+Cs=3C   (3)

Because the capacitance of the bit-line segment 168 during a memory readoperation (Cd+Cs) is expressed in terms of a number of memory cellcapacitances (Cs), Equation (3) may be used to at least estimate thenumber word-lines 132 to activate in the storage array 104 so as toprovide a balanced operation of the sense amplifier 124 a-b.Specifically, Equation (3) estimates the capacitance of the bit-linesegment 168 during a memory read operation to be approximately threetimes the capacitance an individual memory cell 128. Thus, in order tobalance the capacitance on the storage array bit-line segment 168, thecapacitance on the reference array bit-line segment 172 should beapproximately equal to the capacitance of three individual memory cells128. As discussed above, a reference array 108 in accordance with thepresent disclosure may include short bit-line segment lengths as thereference array 108 is typically somewhat narrow. Because the referencearray 108 has a short bit-line segment 172, the capacitance may be smallenough to be ignored or minimized in the balancing calculation. Becausethe capacitance of the bit-line segment 172 may be ignored, the properbalancing capacitance may be added to the bit-line segment by justasserting an appropriate number of word-lines in the reference array172. Thus, following Equation (3), a proper balancing capacitance on thereference array bit-line segment 172 may be achieved by activating threeword-lines 132 in the reference array 172. This process is described ingreater detail in connection with FIG. 4.

FIG. 4 is an illustration a memory device embodiment 400 that shows theactivation of certain word-lines in accordance with the presentdisclosure. As described in greater detail in connection with FIG. 1, amemory device embodiment 400 may include a storage array 404 and areference array 408. Bit-line segments 412 in the reference array 408couple to first sides of sense amplifiers 416 a-b. Bit-line segments 420in the storage array 404 couple to second sides of the sense amplifiers416 a-b. Reference array memory cells 424 are disposed at theintersection of the reference array bit-line segments 412 and referencearray word-lines 428. Storage array memory cells 432 are disposed at theintersection of the storage array bit-line segments 420 and storagearray word-lines 436. FIG. 4 additionally shows an activated storagearray word-line 436 a and a number of activated reference arrayword-lines 428 a. The activated storage array word-line 436 a may beactivated in the process of accessing a particular storage array memorycell 432 a. The activated reference array word-lines 428 a may beactivated to support a balanced operation of the sense amplifier 416 aduring a read operation of other memory access operation. Continuingwith the example above, the memory device 400 may embody a smallernanometer processes such that Vary for the memory device 400 isapproximately 1V. As described, above, the Cd/Cs ratio for such a devicecan be less than or around approximately 2. Thus, a balanced operationof the sense amplifier 416 a may be correspond to the reference arraybit-lines 412 having a capacitance of three individual memory cells.Because the capacitance of the reference array bit-lines 412 itself maybe ignored, the proper balancing capacitance may be, achieved byactivating three reference array word-lines, as indicated in FIG. 4 byreference numeral 428 a.

It should be appreciated that Equation (3) was derived for theparticular of the smaller nanometer example where Vary is aroundapproximately 1V. Given this constraint, the amount of capacitance forthe reference array bit-line segment was determined to be approximatelythree times the amount of capacitance present in an individual memorycell. More generally, Equation (1) may be, used to derive balancingcapacitances for any particular memory arrangement or process. First,Equation (1) may be used to derive a Cd/Cs ratio given the voltagesignal level constraints for a given memory process. Given that thecapacitance on the storage array bit-line segment corresponds toquantity (Cd+Cs), the Cd/Cs ratio may be used to approximate thecapacitance needed for the reference array bit-line segment as multipleof the capacitance of an individual memory cell. The proper balancingcapacitance for the reference array bit-line segment may therefore beachieved by activating a corresponding, number of word-lines in thereference array.

Dummy Word-Line Balancing

The load balancing discussed above generally applies to the operation ofsense amplifiers when word-lines are activated during a memory read orother memory access operation. For example, in the smaller nanometerprocesses, the Cd/Cs ratio may be approximately two. With threeword-lines activated in the reference array, the load will be balancedby Cd+Cs=3Cs because bit-line capacitance is negligible on the referenceside. However, in this same arrangement, the sense amplifier's load maybecome unbalanced during the pre-charge phase because the senseamplifier's load becomes the capacitance of the bit-line capacitance(Cd) only on the activated side.

Present embodiments may use dummy word-lines order o improve the senseamplifier balance during the pre-charge phase. Typically, a word-line rdummy word-line is activated to read out a particular memory cell or tosupport the sense amplifier in such an operation. Thus, a word-line ordummy word-line is typically asserted daring the read out oramplification phase of a memory access operation. In contrast, presentembodiments may activate one or more dummy word-lines during thepre-charge phase and thus out of the typical sequence of memorycomponent activation. By asserting one or more dummy word-lines, presentembodiments may maintain the load on the storage array bit-line segmentat Cd+Cs during the pre-charge phase. In this way, the load on thestorage array bit-line may be maintained at Cd+Cs throughout theoperation of the memory array.

FIG. 5 is an illustration a memory device embodiment 500 that shows theuse of dummy word-lines to improve the sense amplifier balance duringthe pre-charge phase id accordance with the present disclosure. Asdescribed in greater detail in connection with FIG. 1, a memory deviceembodiment 500 may include a storage array 504 and a reference array508. Bit-line segments 512 in the reference array 508 couple to firstsides of sense amplifiers 516 a-b. Bit-line segments 520 in the storagearray 504 couple to second sides of the sense amplifiers 516 a-b.Reference array memory cells 524 are disposed at the intersection of thereference array bit-line segments 512 and reference array word-lines528. Storage array memory cells 532 are disposed at the intersection ofthe storage array bit-line segments 520 and storage array word-lines536. The memory device 500 may additionally include one or more dummymemory cells 540 that are disposed at the intersection of a dummyword-line 544 and a bit-line segment 520.

FIG. 5 also shows an activated storage array word-line 536 a and anumber of activated reference array word-lines 528 a. The activatedstorage array word-line 536 a may be activated in the process ofaccessing a particular storage array memory cell 532 a. The activatedreference array word-lines 528 a may be activated to support a balancedoperation of the sense amplifier 516 a during a read operation of othermemory access operation. Prior to the amplification phase of the memoryaccess operation, the bit-line segments 512, 520 may be pre-chargedduring an equalization phase of the memory access operation. Here, oneor more dummy word-lines 544 may be activated during the pre-chargephase in order to provide a faster and/or more effective equalization.

Continuing with the smaller nanometer process example above, threeword-lines may be activated in the reference array 508 so as to balancethe capacitance of the bit-line segment 512 and the memory cell 532 aduring the amplification phase. In the pre-charge phase, the memory cell532 a is not coupled to the bit-line segment 520 and so does notcontribute to the balancing of the bit-line segment 512 with thebit-line segment 520. In order to compensate for this, a dummy word-line544 may be asserted during the pre-charge phase. The dummy word-line 544is generally asserted when the word-line 536 a is not asserted.Similarly, the word-line 536 a may asserted when the dummy word-line 544is not asserted. Advantages gained by asserting the dummy word-line 544are illustrated in FIG. 6.

FIGS. 6A-B are signal trace diagrams that compare the behavior of anexample memory circuit 500 with and without the use of a dummyword-line. FIGS. 6A-B include a BLT (bit-line true) signal trace 604that corresponds to the bit-line segment 520 associated with the storagearray 504. The BLB (bit-line bar) signal trace 608 corresponds to thebit-line segment 512 associated with the reference array 508. The WL(write line) signal trace 612 corresponds to the word-line 536 a that isasserted to couple the memory cell 532 a to the storage array bit-linesegment 520 in connection with a memory access operation for the memorycell 532 a, FIG. 6A includes an initial phase 616 where the word-line536 a is de-asserted and bit-line segments 512, 520 are pre-charged.Here, the word-line signal trace 612 is low, and the BLT signal trace604 and the BLB signal trace 608 indicate a voltage of Vary/2. Followingthe initial phase 616, a charge sharing phase 620 occurs where theword-line 536 a is asserted and the charge in the desired memory cell532 a is transferred from the, memory cell 532 a to the storage arraybit-line segment 520. Here, the WL signal trace 612 goes from low tohigh and the BLT signal trace 604 rises above Vary/2. Following thecharge-sharing phase 620, an amplification phase 624 occurs where thesense amplifier 516 a amplifies the voltage difference on the bit-linesegments 512, 520. Here, BLT signal trace 604 rises to Vary and the BLBsignal trace 608 falls to Vss. Following the amplification phase 624, apre-charge phase 628 occurs where the word-line 536 a is de-asserted andthe bit-line segments 512, 520 are pre-charged. Here, WL 612 goes low,and the BLT signal 604 and the BLB signal 608 are driven to Vary/2.

FIG. 6A illustrates the behavior of the example memory circuit 500without the use a dummy word-line 544. FIG. 6B illustrates the behaviorof the example memory circuit 500 with the use of a dummy word-line 544.FIG. 6B includes a dummy WL trace 632 that corresponds to the dummyword-line 544. As mentioned, the dummy word-line 544 may be assertedwhen the word-line 536 a is not asserted. Thus, the dummy WL signal 632goes high when the WL signal 612 goes low and vice versa. Thus, thedummy WL signal 632 is de-asserted during the charge-sharing phase 620and the amplification phase 624. In these phases, the total capacitanceon the storage array side of the sense amplifier 515 a corresponds tothe bit-line capacitance plus the desired storage cell capacitance,which total capacitance is balanced by the word-lines 528 a asserted onthe reference array side of the sense amplifier 516 a. In the pre-chargephase 628, this balance is maintained in the absence of the capacitancefrom the desired memory cell 532 a through the capacitance of the memorycell attached to the dummy word-line 544. Without this use of the dummyword-line 544, the sense amplifier operation may become unbalanced duethe capacitive mismatch. As shown in FIG. 5A, the BLB signal 608 mayrise faster than the BLT signal 604 falls. This may result in the BLBsignal overshooting the Vary/2 level. This behavior does not occur whenthe dummy word-line 544 is asserted. As shown in FIG. 6B, the BLT signal604 and the BLB signal 608 change at the same rate. Here, no overshootoccurs and the BLT signal 604 and the BLB signal 608 reach Vary/2faster.

FIG. 5 and FIG. 6 illustrate the use of dummy words lines in theoperation of a sense amplifier that is arranged between a referencearray and a storage array. As shown in FIG. and FIG. 8, this concept canbe extended to include the operation of a sense amplifier that is,arranged between two storage arrays. In some conventional memory deviceschemes, a non-negligible imbalanced sense amplifier occurs at smallCd/Cs ratios. For example, some conventional memory device schemes mayhave zero offsets as high as 20% to 30% of the sense amplifier signalamount. In order to overcome this difficultly and to keep the senseamplifier's load balanced throughout the various phases of the memorydevice operation, one or more dummy word-lines may activated reverselyin one or more storage arrays, as shown in Table (1) below. Here, eithera word-line-or a dummy word is activated in a given time. Because aword-line is activated at any given time, the sense amplifier's loadbecomes Cd+Cs at all times and on both sides of the sense amplifier.Also, this operation provides write line coupling-noise reduction sothat the sense amplifier's operational margin is, improved by adding upits effect on the sense amplifier's load balance. Finally, thistechnique helps bit-line extension due to improvement in senseamplifier's operation margin. Specifically, this technique may cancelthat offset of the reference side.

TABLE 1 conventional embodiment activated sec referece sec activated secreference sec @Active Cd + Cs Cd Cd + Cs Cd + Cs @EQ Cd Cd Cd + Cs Cd +Cs

FIG. 7 is an illustration a memory device embodiment 700 that includesthe use of dummy word-lines in adjacent storage arrays to improve thesense amplifier balance during the pre-charge phase in accordance withthe present disclosure. A memory device embodiment 700 may include afirst storage array 704 and a second storage array 708. Bit-linesegments 712 in the first storage array 704 couple to first sides ofsense amplifiers 716 a-b. Bit-line segments 720 in the second storagearray 708 couple to second sides of the sense amplifiers 716 a-b. Firststorage array memory cells 724 are disposed at the intersection of thefirst storage array bit-line segments 712 and the first storage arrayword-lines 728. Second storage array memory cells 732 are disposed atthe intersection of the second storage array bit-line segments 720 andsecond storage array word-lines 736.

The first storage array 704 may include at least one dummy word-line 740that is, disposed at the intersection of a dummy word-line 744 and abit-line segment 712. In one respect, the dummy word-line 740 may beactivated to provide balancing capacitance for the sense amplifier 716a-b during a memory access operation directed to the second storagearray 708. For example, a particular second, storage array memory cell732 a may be accessed via a memory access operation that includesactivating the corresponding storage array word line 736 a. In thismemory access operation, the first storage array 704 is the “reference”side of the sense amplifier 716 a, and the second storage array 708 isthe “activated” side of the sense amplifier 716 a. Here, the dummyword-line 740 may be activated to balance the capacitance present on thesecond bit-line segment 720 due to the storage array memory cell 732 a.

Similarly, the second storage array 708 may include at least one dummyword-line 748 that is disposed at the intersection of a dummy word-line752 and a bit-line segment 720. In one respect, the dummy word-line 748may be activated to provide balancing capacitance for the senseamplifier 716 a-b during a memory access operation directed to the firststorage array 704. For example, a particular first storage array memorycell 724 a may be accessed via a memory access operation that includesactivating the corresponding storage array word-line 728 a. In thismemory access operation, the first storage array 704 is, the “activated”side of the sense amplifier 716 a, and the second storage array 708 isthe “reference” side of the sense amplifier 716 a. Here, the dummyword-line 748 may be activated to balance the capacitance present on thefirst bit-line segment 712 due to the storage array memory cell 724 a.

Prior to the amplification phase of the memory access operation, thebit-line segments 712, 720 may be pre-charged during an equalizationphase of the memory access operation. Here, one or more dummy word-linesmay be activated during the pre-charge phase in order to provide afaster and/or more effective equalization. In one example, one dummyword-line 740 in the first storage array 704 is activated during theequalization phase. To balance the capacitance from this dummy word-line740, one dummy word-line 748 in the second storage array 708 is alsoactivated during the equalization phase. Thus, in accordance withpresent embodiments, various dummy word-lines may be activated in boththe amplification phase and the equalization phase.

FIGS. 8A-B are signal trace diagrams that compare the behavior of anexample memory circuit 700 with and without the use of a dummyword-line. By way of example, the memory access operation illustrated inFIGS. 8A-B is one where the first storage array 704 is the “activated”side of the sense amplifier 716 a, and the second storage array 708 isthe “reference” side of the sense amplifier 716 a. FIGS. 8A-B include aBLT (bit-line true) signal trace 804 that corresponds to the bit-linesegment 712 associated with the first storage array 704. The BLB(bit-line bar) signal trace 808 corresponds to the bit-line segment 720associated with the second storage array 708. The WL1 (write line 1)signal trace 812 corresponds to the word-line 728 a that is asserted tocouple, the memory cell 724 a to the first storage array bit-linesegment 712 in connection with a memory access operation for the memorycell 724 a.

FIG. 8A-B includes an initial phase 816 where the word-line 728 a isde-asserted and bit-line segments 712, 720 are pre-charged. Here, theword-line signal trace 728 a is low, and the BLT signal trace 804 andthe BLB signal trace 808 indicate a voltage of Vary/2. Following theinitial phase 816, a charge sharing phase 820 occurs where the word-line728 a is asserted and the charge in the desired memory cell 724 a istransferred from the memory cell 724 a to the storage array bit-linesegment 712. Here, the WL1 signal trace 812 goes from low to high andthe BLT signal trace 804 rises above Vary/2. Following thecharge-sharing phase 820, an amplification phase 824 occurs where thesense amplifier 716 a amplifies the voltage difference on the bit-linesegments 712, 720. Here, BLT signal trace 804 rises to Vary and the BLBsignal trace 808 falls to Vss. Following the amplification phase 824, apre-charge phase 828 occurs where the word-line 728 a is de-asserted andthe bit-line segments 712, 720 are pre-charged. Here, WL1 signal 812goes low, and the BLT signal 804 and the BLB signal 808 are driven toVary/2.

FIG. 8A illustrates the behavior of the example memory circuit 700without the use a dummy word-line 748, FIG. 8B illustrates the behaviorof the example memory circuit 700 with the use of a dummy word-line 740in the first storage array 704 and a dummy word-line 748 in the secondstorage array 708, FIG. 8B includes a dummy WL1 trace 832 thatcorresponds to the dummy ward-line 740 in the first storage array 704.As mentioned, the dummy word-line 740 may be asserted when the word-line728 a is not asserted. Specifically, the dummy WL1 signal 832 goes highwhen the WL signal 812 goes low and vice versa. Thus, the dummy WL1signal 832 is asserted during the initial phase 816 and the pre-chargephase 828. The dummy WL1 signal 832 is de-asserted during thecharge-sharing phase 820 and the amplification phase 824. FIG. 8B alsoincludes a dummy WL2 trace 836 that corresponds to the dummy word-line748 in the second storage array 708. The dummy word-line 748 in thesecond storage array 708 may be asserted when the word-line 728 a isasserted. The dummy word-line 748 may also be asserted when the dummyword-line 740 in the first storage array 704 is asserted. Specifically,the dummy word-line 748 in the second storage array 708 may be assertedduring the charge-sharing phase 820 and the amplification phase 824.Thus, the dummy WL2 signal 836 is asserted during the initial phase 816,the charge-sharing phase 820, the amplification phase 824, and thepre-charge phase 828.

In the charge-sharing phase 820 and the amplification phase 824, thetotal capacitance on the first storage array 704 side of the senseamplifier 716 a corresponds to the capacitance of the first bit-line 712plus the desired storage cell 724 a capacitance. This total capacitanceis balanced by the second bit-line 720 plus the capacitance added by thedummy word-line 748 of the second storage array 708. In the pre-chargephase 828, this balance is maintained m the absence of the capacitancefrom the desired memory cell 724 a through the capacitance added by thedummy word-line 740 of the first storage array 704. This use of dummyword-lines 740, 748 enables the voltage on the bit-lines 712, 720 toequalize faster. Thus, as shown, the BLT signal 804 and the BLB signal808 reach the equalization voltage of Vary/2 faster in FIG. 8B than theydo in FIG. 8A.

Test Modes

Equation (1) may be used as described above to determine a number ofword-lines to be activated in a reference array so as to providebalanced sense amplifier operation during a read operation or othermemory access operation. However, the number derived using this processmay be approximate and so may not exactly correspond to an, optimalnumber of activated word-lines in a given memory device. Thus, a memorydevice may be manufactured with slightly more reference array word-linesthat is indicated by Equation (1). Once such a device is manufactured,the device may undergo a testing procedure that determines moreprecisely the optimal number of reference array word-lines to beactivated so as to provide a balanced sense amplifier operation,

FIG. 9 is a flow chart 900 that provides an example test flow inaccordance with present embodiments. The example test flow of FIG. 9includes operations for determining an optimal number of activatedword-lines in a memory device 100 having at least one reference array108 in accordance with present embodiments. Initially, in operation 904,a contact check may be executed so as to determine the operationalstatus of the pads or other external contacts associated with the memorydevice 100. In operation 908, a power level check may be executed so todetermine the operational status of power supply components and contactsassociated with the memory device 100. In operation 912, an equalizationlevel check may be executed so as to determine the optimal number ofactivated word-lines for one or more reference array associated with thememory device 100. A first example system and method for preforming anequalization level check is described below in connection with FIGS. 1C,10-11A-B. A second example system and method for preforming anequalization level check is described below in connection with FIGS.12-13A-B. In operation 916, a sense amplifier offset check may beexecuted so as to determine if any particular word-line in the referencearray is malfunctioning and needs to be replaced. An example system andmethod for preforming a sense amplifier offset check is described belowin connection with FIGS. 14-15A-B. In operation 920, repairs and/ormodifications may be made to the memory device under test. In operation924 the probe test flow process may end. Once the test flow hascompleted, the particular “always activated” word lines may selected foruse in the final product.

Referring again to FIG. 1C, which, as mentioned, is a schematic of theexample memory device 100 that shows individual memory cells within anumber of memory arrays. FIG. 1C additionally includes an illustrationof a tester embodiment 1002 a for a memory device 100 in accordance withthe present disclosure. The tester 1002 a may be used for anequalization level check of a memory device 100 in accordance with thepresent disclosure. FIG. 11B is a timing diagram that shows varioussignal traces that illustrate the equalization level check for theexample memory device 100. As mentioned in connection with operation 912above, an equalization level check may be executed so as to determinethe optimal number of activated word-lines for one or more referencearrays associated with a memory device. As described in greater detailin connection with FIGS. 1A-C, a memory device embodiment 100 mayinclude a storage array 104 and a reference array 108. Bit-line segments172 in the reference array 108 couple to first ides of sense amplifiers124. Bit-line segments 168 in the storage array 104 couple to secondsides of the sense amplifiers 124. Reference array memory cells 128 aredisposed at the intersection of the reference array bit-line segments172 and reference array word-lines 132. A reference array word decoder116 a is configured to selectively activate and de-activate thereference array word-lines 132 (See reference number 1105 in FIG. 11B).Storage array memory cells 128 are disposed at the intersection of thestorage array bit-line segments 168 and storage array word-lines 132. Astorage array word decoder 116 b is configured to selectively activateand de-activate the storage array word-lines 132.

The tester 1002 a may include a test mode option signal (TmEdgeFz) 1048that is coupled to a word decoder 116 a associated with the referencearray 108. The word decoder 116 a may be configured to activatecombinations of word-lines 132 in the reference array 108. Morespecifically, the word decoder 116 a may assert or de-assert theword-lines 132 in the reference array 108 in combinations specified byinputs to the word decoder 116 a. In test mode, the test mode optionsignal 1048 may provide input to word decoder 116 a and, in so doing,selectively activate the word-lines 132 in the reference array 108. Insome implementations, the test mode option signal 1048 has one signalline per signal line in the word decoder 116 a output. Here, a word-line116 a is activated by the assertion of a corresponding signal line inthe test mode option signal 1048.

The tester 1002 a may also include a power amplifier enable signal(VBLR) 1052 that is configured to enable and disable a power amplifierassociated with the sense amplifiers 124. Referring to the example senseamplifier 200 of FIG. 2, the power amplifier enable signal 1052 may becoupled to the VBLP power supply 216 that is coupled to the secondtransistor group 224, specifically to the first n-channel transistor 228a and to the third n-channel transistor 228 b. The power amplifierenable signal 1052 may be asserted to enable the VBLP power supply 216.When enabled, the VBLP power supply 216 may power the first n-channeltransistor 228 a and the third n-channel transistor 228 c so as toequalize the first bit-line 204 a and the second bit-line 204 b asdescribed about in connection with FIG. 2. The power amplifier enablesignal 1052 may be de-asserted to disable to VBLP power supply 216. Whenthe VBLP power supply 216 is disabled, the first n-channel transistor228 a and the third n-channel transistor 228 c are removed from thecircuit and the first bit-line 204 a and the second bit-line 204 b areshorted together. Thus, with VBLP power supply 216 disabled, the senseamplifier enters a “voltage sharing” mode where voltage is sharedbetween the first and second sides of the sense amplifier 200 (Seereference number 1109 in FIG. 11B).

The tester 1002 a may also include an equalization signal (BLEQf) 1056that is configured to enable an equalization function of the senseamplifiers 124 (See reference number 1113 in FIG. 11B). Referring to theexample sense amplifier 200 of FIG. 2, the equalization signal 1056 maycorrespond to the BLEQ signal 232 that is connected to the gates of thetransistors in the first group 220, specifically the first n-channeltransistor 228 a, the second n-channel transistor 228 b, and the thirdn-channel transistor 228 c.

The tester 1002 a may also include a bit-line merge signal (TmBLMerge)1060 that is configured to enable various components that together mergeand provide output from a number of bit-line segments (See referencenumber 1117 in FIG. 11B). Here, the bit-line merge signal 1060 may becoupled components of a transistor edge network 1068. The edge network1068 may include a plurality of bit-line transistors 1072. Each of thebit-line transistors 1072 is connected to one of the reference arraybit-lines segments 172. As shown in FIG. 1C, the bit-line transistors1072 may be connected in parallel. Alternatively, (as described ingreater detail in connection with FIG. 10) the bit-line transistors 1072may be connected in series. The bit-line merge signal 1060 provides thegate signal for each of the bit-line transistors 1072. Through thisconfiguration, the edge network 1068 may be generally configured toreceive merged bit-line output (See reference number 1121 in FIG. 11B)and to further merge that input into a bundled output signal 1076 (Seereference number 1125 in FIG. 11B). More specifically, the bit-linetransistors 1072 receive merged bit-line output from each bit-line inthe reference array 108 and, when enabled by the bit-line merge signal1060, join those outputs together into a bundled output 1076.

The tester 1002 a may additionally include a comparator 1080 having afirst input that is configured to receive the bundled output 1076. Asecond input of the comparator may couple to a reference voltage, whichin one embodiment is VBLR. The comparator 1080 may be configured tocompare the bundled output signal 1076 to the reference voltage and toprovide a responsive output signal at a comparator output 1084. Thetester 1002 a may then provide the edge comparator 1080 output on aglobal bit (MIO) line through a dedicated edge output pathway thatbypasses the RWAMP circuits 1088 associated with, the memory device 100.Control circuits for the RWAMP circuits are described in greater detailbelow in connection with FIGS. 18A-B. In one embodiment, the comparatoroutput 1084 provides either a high or low signal based on a comparisonof its inputs. A high output signal may correspond to the first inputsignal being greater than the second input signal. A low output signalmay correspond to the second input signal being greater than the firstinput signal. By placing the comparator 1080 outside of and/or adjacentto the memory array 100, the accuracy of the test signal is improved atleast because unwanted parasitic elements are reduced.

FIG. 10 is schematic illustration of an example memory device thatincludes an alternative tester 1002 b configuration. Like the tester1002 a illustrated in FIG. 1C, the tester 1002 b of FIG. 10 may be usedfor an equalization level check of a memory device 100 in accordancewith the present disclosure. Like the tester 1002 a, the tester 1002 bmay include a test mode option signal (TmEdgeFz) 1048 that is coupled toa word decoder 116 a associated with a reference array 108, a poweramplifier enable signal (VBLR) 1052 that is configured to enable anddisable a power amplifier associated with sense amplifiers 124, and anequalization signal (BLEQf) 1056 that is configured to enable anequalization function of the sense amplifier 124. These signals andcomponents are described in greater detail above in connection with FIG.1C.

The tester 1002 b may also include a bit-line merge signal (TmBLMerge)1060 that is, configured to enable various components that togethermerge and provide output from a number of bit-line segments. Here, thebit-line merge signal 1060 may be coupled to the gate of an outputtransistor 1064, which is a component of a transistor edge network 1068.In addition to the output transistor 1064, the edge network 1068includes n plurality of bit-line transistors 1072. Each of the bit-linetransistors 1072 is connected to one of the reference array bit-linessegments 172. The bit-line transistors 1072 are connected in series suchthat they are connected at one end to the output transistor 1064. Thebit-line merge signal 1060 provides the gate signal for each of theoutput transistors 1064. Through this configuration, the edge network1068 may be generally configured to receive merged bit-line output andto further merge that input into a bundled output signal 1076. Morespecifically, the bit-line transistors 1072 receive merged bit-lineoutput from each bit-line in the reference array 1008 and, when enabledby the bit-line merge signal 1060, join those outputs together into abundled output 1076 that is output by the output transistor 1064.

The tester 1002 b may additionally include a comparator 1080 having afirst input that is coupled to the second end of the output transistor1064. A second input of the comparator may couple to a referencevoltage, which in one embodiment is VBLR. The comparator 1080 may beconfigured to compare the bundled output signal 1076 provided by theoutput transistor 1064 to the reference voltage and to provide aresponsive output signal at a comparator output 1084. The tester 1002 bmay then provide the edge comparator 1080 output on a global bit (MIO)line through an output pathway that includes the RWAMP circuits 1088associated with the memory device 100. In one embodiment, the comparatoroutput 1084 provides either a high or low signal based on a comparisonof its inputs. A high output signal may correspond to the first inputsignal being greater than the second input signal. A low output signalmay correspond to the second input signal being greater than the firstinput signal. By placing the comparator 1080 outside of and/or adjacentto the memory array 100, the accuracy of the test signal is improved atleast because unwanted parasitic elements are reduced,

FIG. 11A is a flow chart 1100 that illustrates a test-mode that executesa check of equalization levels in accordance with a first embodiment.The test mode illustrated in FIG. 11A may be executed using the tester1002 a illustrated in FIG. 1C. Alternatively, the test mode illustratedin FIG. 11 may execute using the tester 1002 b illustrated in FIG. 10.The test-mode generally adjusts a load balance for bit-line pairs on theedge sense amplifier region by selecting the always activated word-linesin the edge array. As mentioned, “always activated” word-lines areactivated during each memory access operation so as to add balancingcapacitance. The tester 1002 a-b generally operates by finding a loadbalanced option by changing a number of activated word-lines in the edgearray. More specifically, the tester loops through a set of testprocedure steps until an optimal number of word-lines is found.

In operation 1104, the tester 1002 a-b sets a proposed test-mode entry.The proposed test-mode entry generally corresponds to a particularcombination of activated word-lines 132 in the reference array 108. On afirst pass through the set of test procedure steps, the proposedtest-mode entry may correspond to only one word-line 132 being asserted.On successive passes through the set of test procedure steps, additionalword-lines 132 may be added such that progressively more word-lines 132are included in the test-mode entry. For example, one word-line 132 maybe activated on the first pass, two word-lines 132 may be activated onthe second pass, three word-lines 132 may be activated on the thirdpass, and so on. As mentioned, particular combinations of word-lines 132may be activated via the test mode option signal 1048. Thus, inoperation 1104, the tester 1002 a-b asserts an appropriate combinationof signals on the test mode option signal 1048 depending on the numberof passes through the test mode procedure that have taken place so far.Based on this signal, the appropriate number of word-lines 132 in thereference array 108 are activated via the operation of the referencearray word decoder 116 a.

In operation 1108, the tester 1002 a-b activates one word-line 132 inthe adjacent storage array 104. In so doing, the tester 1002 a-bprepares the storage array 104 for a write operation on the activatedword-line 132. The tester 1002 a-b may provide an appropriate controlsignal to the storage array word decoder 116 a. Based on the inputcontrol signal, the storage array word decoder 116 a may assert thedesired word-line 132 in the storage array 104. With the desiredword-line asserted 132, the various memory cells on the word-line 132couple to the word-line through the operation of an access transistor asdescribed in connection with FIGS. 1A-C. With the memory cells socoupled, the storage array 104 is prepared for a write operation on theactivated word-line 132.

In operation 1112, the tester 1002 a-b writes the same data for allcolumn addresses in the storage array 104. More specifically, the tester1002 a-b asserts the same data on all of the bit-lines 168 in thestorage array 104. This memory write operation may be executed via thebit decoder discussed above in connection with FIGS. 1A-C. In oneembodiment, the tester 1002 a-b executes the memory write through anappropriate memory operation such as a Y-scan operation or the like.Additionally, in operation 1112, the tester 1002 a-b turns off the VBLPpower supply 216. As mentioned, this may be achieved by de-asserting thepower amplifier enable signal 1052. With the VBLP power supply 216turned-off, the reference side of the sense amplifiers 1016 sets to thereversed data and VBLP's source-line (VBLsr) sets to floating Vary/2.

In operation 1116, the tester 1002 a-b executes the proposed test-modeentry by asserting the bit-line merge signal 1060. While keeping theword-lines active, the tester 1002 a-b asserts the bit-line equalizationsignal 1056 to short/merge multi bit-lines 172 in the reference array108 with bit-lines 168 in the storage array 104. The shorted bit-linesare then output through the edge bit-line that are bundled togetherthrough the bit-line transistors 1072. This output may be received atthe comparator 1080 that is disposed outside of and/or adjacent to thememory array 100. In a configuration such as shown in FIG. 10 where thebit-line transistors 1072 are connected in series, bundled output fromthe bit-line transistors 1072 may be provided to an output transistor1064, which, in turn provides output to the comparator 1080.

In operation 1120, the tester 1002 a-b provides the output signal 1084of the edge comparator 1080 on a global bit (MIO) line. In theembodiment of FIG. 1C the tester 1002 a provides the edge comparator1080 output on a global bit (MIO) line through a dedicated edge outputpathway that bypasses the RWAMP circuits 1088 associated with the memorydevice 100. In the embodiment of FIG. 10, the tester 1002 b provides theedge comparator 1080 output on a global bit (MIO) line through an outputpathway that includes the RWAMP circuits 1088 associated with the memorydevice 100. As described in connection with FIG. 2, a global bit-lineconnects to data readout circuits that are coupled to or otherwiseassociated with a memory device. Generally, data is write in and readout of the memory device by being written across the global bit-linesand into and out of an individual memory cells. This data pathway mayalso be used to read test data out of the memory device. Thus, inoperation 1120, the tester 1002 a-b makes use of the data pathway andreads out test data across the global bit-lines. In some cases, thetester 1002 a-b may execute a delay prior providing the output signal1084 in order to allow the output signal levels to stabilize. Forexample, the tester 1002 a-b may wait a few micro seconds for signallevels to stabilize.

In operation 1124, the tester 1002 a-b may determine if additionaltesting is required. More specifically, the tester 1002 a-b maydetermine if an additional pass through the set of test procedure stepsis needed. This determination may be based on whether or not a change inoutput signal 1084 is detected. A change in the output signal 1084 mayoccur when the output swings from either high to low or from low tohigh. When either of these two transistors occurs, it may be determinedthat the capacitance on the bit-lines 168, 172 is substantiallybalanced. At this point, the optimal number of always activatedword-lines is determined.

If additional testing is required, operation 1128 follows operation1124. In operation 1128, the tester 1002 a-b sets a new proposed testmode entry option for the test mode option signal 1048. Operation 1104follows operation 1128 such that the test flow is repeated with the newtest mode entry option. If no additional testing is required, operation1132 follows operation 1124. In operation 1132, the tester ends the testflow.

FIG. 12 is an illustration a tester embodiment 1202 for a memory device1200 in accordance with the present disclosure. The tester 1202 may beused for an equalization level check of a memory device 1200 inaccordance with the present disclosure. FIG. 13B is a timing diagramthat shows various signal traces that illustrate the equalization levelcheck for the example memory device 100. As mentioned in connection withoperation 912 above, an equalization level check may be executed so asto determine the optimal number of activated word-lines for one or morereference arrays associated with a memory device. The tester 1202 may beused implemented as an alternative to the test-mode for equalizationlevel checking of FIG. 1C and FIG. 10. The tester 1202 may be configuredto adjust edge dummy memory cell capacitance in connection with a normalread operation. Here, the tester 1202 may use RWAMP circuits that areshared between normal operation circuits and test operations circuitsbased on an input selector.

As mentioned, an equalization level check may be executed so as todetermine the optimal number of activated word-lines for one or morereference arrays associated with a memory device. As described ingreater detail in connection with FIGS. 1A-C, a memory device embodiment1200 may include a storage array 104 and a reference array 108. Bit-linesegments 172 in the reference array 108 couple to first sides of senseamplifiers 124. Bit-line segments 168 in the storage array 104 couple tosecond sides of the sense amplifiers 124. Reference array memory cells128 are disposed at the intersection of the reference array bit-linesegments 172 and reference array word-lines 132. A reference array worddecoder 116 a is configured to selectively activate and de-activate thereference array word-lines 132. Storage array memory cells 128 aredisposed at the intersection of the storage array bit-line segments 168and storage array word-lines 132. A storage array word decoder 116 b isconfigured to selectively activate and de-activate the storage arrayword-lines 128.

The memory device 1200 may additionally include a first global bit-line(MIO) 1238 and second global bit-line (MIO) 1242. As described ingreater detail in connection with FIG. 2, global bit-lines 1238, 1242may be associated with the sense amplifiers 124 may connect to the datareadout circuits that are coupled to or otherwise associated with thememory device 1200. Generally, data is written in and read out of thememory device 1200 by being written across the global bit-lines 1238,1242 and into and out of an individual memory cells. This data pathwaymay also be used to read test data out of the memory device as describedin greater detail below.

The tester 1202 may include a test mode option signal (TmEdgeFz) 1248, apower amplifier enable signal (VBLsr) 1252, an equalization signal(BLEQf) 1256 (See reference number 1305 in FIG. 13B), and a bit-linemerge signal (TmBLMerge) 1260 (See reference number 1309 in FIG. 13B).As described in more detail in connection with FIG. 1C and FIG. 10, thetest mode option signal (TmEdgeFz) 1248 is coupled to a word decoder 116associated with the reference array 108 and is configured to drive theword decoder 116 a with various test mode inputs. The power amplifierenable signal (VBLsr) 1252 is configured to enable (See reference number1313 in FIG. 13B) and disable (See reference number 1317 in FIG. 13B) apower amplifier associated with the sense amplifiers 124. Theequalization signal (BLEQf) 1256 is configured to enable an equalizationfunction of the sense amplifiers 124. The bit-line merge signal(TmBLMerge) 1260 that is configured to enable various components thattogether merge (See reference number 1321 in FIG. 13B) and provideoutput (See reference number 1325 in FIG. 13B) from a number of bit-linesegments.

In the embodiment of FIG. 12, the bit-line merge 1260 may be coupled toa at least one of a number of transfer gates 1268, which transfer gate1268 is preceded by an AND gate 1272. Each of the transfer gates 1268 isconnected to one of the global bit-lines 1238, 1242 to thereby couplethe RWAMP circuits 1288 to the sense amplifiers 124. The bit-line mergesignal 1260 combines with an enable signal 1270 from the row decoder 116b through the AND gate 1272 to provide the gate signal (See referencenumber 1329 in FIG. 13B) for the transfer gate 1268 associated with thereference array 108. Through this configuration, the transfer gate 1268may be generally configured to provide input to the RWAMP circuits 1288,which in turn generates global bit-line output (See reference number1333 in FIG. 13B). More specifically, the transfer gate 1268 receivesbit-line output from the sense amplifiers 124 in the memory device 1200.When the transfer gate 1268 associated with the reference array 108 isenabled by the bit-line merge signal 1260 in test mode, this transfergate 1268 joins those outputs together into a bundled output that isprovided to the RWAMP circuit 1288.

The transfer gates 1268 are connected so as to form a portion of thenormal data output path to the RWAMP circuits 1288. The normal dataoutput path includes the RWAMP circuits 1288, which are coupled on oneend to a DQ pad. On an opposite end, the RWAMP circuits 1288 are coupledto a bit-line transistor network through the transfer gates 1286. Thetransfer gate 1268 associated with the reference array 108 is generallyconfigured to pass either the test mode data or normal data output basedon the state of output provided by the AND gate 1272. In test mode, thetransfer gate 1268 associated with the reference array 108 passesbundled test data output from the reference array 108. In normal mode,the transfer gate 1268 associated with the reference array 108 passesnormal data readouts.

The RWAMP circuits 1288, which is part of the normal data output path,may function similarly to the comparator 1080 discussed in connectionwith FIG. 1C and FIG. 10. Specifically, the RWAMP circuits 1288 may beconfigured to compare the bundled output signal provided by the transfergate 1268 associated with the reference array 108 to the referencevoltage and to provide a responsive output signal that is provided asinput to the DQ pad. In one embodiment, a RWAMP circuit 1288 provideseither a high or low signal based on a comparison of its inputs. A highoutput signal may correspond to the first input signal being greaterthan the second input signal. A low output signal may correspond to thesecond input signal being greater than the first input signal.

FIG. 13A is a flow chart 1300 that illustrates a test-mode that executesa check of equalization levels in accordance with a second embodiment.The test mode illustrated in FIG. 13 may be executed using, the tester1202 illustrated in FIG. 12. The test-mode generally adjusts a loadbalance for bit-line pairs on the edge sense amplifier region byselecting the always activated word-lines in the edge array. Asmentioned, “always activated” word-lines are activated during eachmemory access operation so as to balancing capacitance. The tester 1202generally operates by finding a load balanced option by changing anumber of activated word-lines in the edge array. More specifically, thetester loops through a set of test procedure steps until an optimalnumber of word-lines is found.

In operation 1304, the tester 1202 sets a proposed test-mode entry. Theproposed test-mode entry generally corresponds to a particularcombination of activated word-lines 132 in the reference array 108. On afirst pass through the set of test procedure steps, the proposedtest-mode entry may correspond to only one word-line 132 being asserted.On successive passes through the set of test procedure steps, additionalword-lines 132 may be added such that progressively more word-lines 132are included in the test-mode entry. For example, one word-line 132 maybe activated on the first pass, two word-lines 132 may be activated onthe second pass, three word-lines 132 may be activated on the thirdpass, and so on. As mentioned, particular combinations of word-lines 132may be activated via the test mode option signal 1248. Thus, inoperation 1304, the tester 1202 asserts an appropriate combination ofsignals on the test mode option signal 1248 depending on the number ofpasses through the test mode procedure that have taken place so far.Based on this signal, the appropriate number of word-lines 132 in thereference array 108 are activated via the operation of the referencearray word decoder 116 a.

In operation 1308, the tester 1202 activates one word-line 132 in theadjacent storage array 104. In so doing, the tester 1202 prepares thestorage array 104 for a write operation on the activated word-line 132.The tester 1202 may provide an appropriate control signal to the storagearray word decoder 116 b. Based on the input, control signal, thestorage array word decoder 116 b may assert the desired word-line 132 inthe storage array 104. With the desired word-line asserted 132, thevarious memory cells on the word-line 132 couple to the word-linethrough the operation of an access transistor as described in connectionwith FIGS. 1A-C. With the memory cells so coupled, the storage array 104is prepared for a write operation on the activated word-line 132.

In operation 1312, the tester 1202 writes the same data for all columnaddresses in the storage array 104. More specifically, the tester 1202asserts the same data on all of the bit-lines 168 in the storage array104. This memory write operation may be executed via the bit decoderdiscussed above in connection with FIGS. 1A-C. In one embodiment, thetester 1202 executes the memory write through an appropriate memoryoperation such as a Y-scan operation or the like. Additionally, inoperation 1312, the tester 1202 turns off the VBLP power supply 216. Asmentioned, this may be achieved by de-asserting the power amplifierenable signal 1252. With the VBLP power supply 216 turned-off, thereference side of the sense amplifiers 1216 sets to the reversed dataand VBLP's source-line (VBLsr) sets, to floating Vary/2.

In operation 1316, the tester 1202 executes the proposed test-mode entryby asserting the bit-line merge signal 1260. While keeping theword-lines active, the tester 1202 asserts the bit-line equalizationsignal 1256 to short/merge multi bit-lines 172 in the reference array108 with bit-lines 168 in the storage array 104. The shorted bit-linesare then prepared for output through the transfer gate 1268 to the RWAMPcircuits 1288.

In operation 1320, the tester 1202 executes a read operation afterswitching the input of the RWAMP circuits 1288 from the normal readcircuits to the test circuits. Specifically, in test mode, the transfergate 1268 associated with the reference array 108, when enabled throughthe AND,gate 1272, passes bundled test data output from the referencearray 108. In executing the read operation, output is provided to the DQpad as part of the normal read out path. In some cases, the tester 1302may execute a delay prior providing the output signal on the globalbit-line in order to allow the output signal levels to stabilize. Forexample, the tester 1202 may wait a few micro seconds for signal levelsto stabilize.

In operation 1324, the tester 1202 may determine if additional testingis required. More specifically, the tester 1302 may determine if anadditional pass through the set of test procedure steps is needed. Thisdetermination may be based on whether or not a change in output signalis detected. A change in the output signal may occur when the outputswings from either high to low or from low to high. When either of thesetwo transistors occurs, it may be may be determined that the capacitanceon the bit-lines 168, 172 is substantially balanced. At this point, theoptimal number of always activated word-lines is determined.

If additional testing is required, operation 1328 follows operation1324. In operation 1328, the tester 1202 sets a new proposed test modeentry option for the test mode option signal 1248. Operation 1304follows operation 1328 such that the test flow is repeated with the newtest mode entry option. If no additional testing is required, operation1332 follows operation 1324. In operation 1332, the tester ends the testflow.

FIG. 14 is an illustration a tester embodiment 1402 for a memory device1400 in accordance with the present disclosure. The tester 1402 may beused for sense amplifier offset checking in a memory device 1400 inaccordance with the present disclosure. FIG. 15B is a timing diagramthat shows various signal traces that illustrate the sense amplifieroffset checking for the example memory device 1400. As mentioned inconnection with operation 916 above, a sense amplifier offset check maybe executed so as to reject defective word-lines. In someimplementations, a sense amplifier offset check may reject defectiveword-lines in combination with a functional test, DC test, and so on.

As described in greater detail in connection with FIG. 1, a memorydevice embodiment 1400 may include a storage array 1404 and a referencearray 1408. Bit-line segments 1412 in the reference array 1408 couple tofirst sides of sense amplifiers 1416. Bit-line segments 1420 in thestorage array 1404 couple to second sides of the sense amplifiers 1416.Reference array memory cells 1424 are disposed at the intersection ofthe reference array bit-line segments 1412 and reference arrayword-lines 1428. A reference array word decoder 1432 is configured toselectively activate and de-activate the reference array word-lines1428. Storage array memory cells 1436 are disposed at the intersectionof the storage array bit-line segments 1420 and storage array word-lines1440. A storage array word decoder 1444 is configured to selectivelyactivate and de-activate the storage array word-lines 1436.

The tester 1402 may include a test mode option signal (TmEdgeFz) 1448, apower amplifier enable signal (VBLsr) 1452, an equalization signal(BLEQf) 1456, and a bit-line merge signal (TMBLMerge) 1460 (Seereference number 1505 in FIG. 15B). As described in more detail inconnection with FIG. 1C and FIG. 10, the test mode option signal(TmEdgeFz) 1448 is coupled to a word decoder 1432 associated with thereference array 1408 and is configured to drive the word decoder 1432with various test mode inputs. The power amplifier enable signal (VBLsr)1452 is configured to enable (See reference number 1509 in FIG. 15B) anddisable (See reference number 1513 in FIG. 15B) a power amplifierassociated with the sense amplifiers 1416. The equalization signal(BLEQf) 1456 is configured to enable an equalization function of thesense amplifiers 1416.

The tester 1402 may also include a bit-line merge signal (TmBLMerge)1460 that is configured to enable various components that together merge(See reference number 1517 in FIG. 15B) and provide output (Seereference number 1521 in FIG. 15B) from a number of bit-line segments.Here, the bit-line merge signal 1460 may be configured to gate theequalization signal 1456 such that the bit-line merge signal 1460 may beasserted to pass the equalization signal 1456 to the sense amplifiers1416. The bit-line merge 1460 may also be coupled to the gate of anoutput transistor 1464, which is a component of a transistor edgenetwork 1468. In addition to the output transistor 1464, the edgenetwork 1468 includes a plurality of bit-line transistors 1472. Each ofthe bit-line transistors 1472 is connected to one of the reference arraybit-lines segments 1412. The bit-line transistors 1472 are connected inseries such that they are connected at one end to the output transistor1464. The bit-line merge signal 1460 provides the gate signal (Seereference number 1525 in FIG. 15B) for each of the output transistors1464. Through this configuration, the edge network 1468 may be generallyconfigured to receive merged bit-line output and to further merge thatinput into a bundled output signal 1476. More specifically, the bit-linetransistors 1472 receive merged bit-line output from each bit-line inthe reference array 1408 and, when enabled by the bit-line merge signal1460, join those outputs together into a bundled output 1476 that isoutput by the output transistor 1464.

As shown in FIG. 14, a tester may additionally include an edgeequalization signal (TmEdgeEq) 1480. The edge equalization signal 1480is coupled to a first end of the transistor edge network 1468. The edgeequalization signal 1480 is generally configured to provide a voltagethat differs by a small amount from the VBLP voltage associated with thesense amplifier 1416. The edge equalization signal 1480 may includeinputs that specify the amount by which the edge equalization signal1480 differs from the VBLP voltage. As described below, the tester 1402may assert a voltage with a range defined by VBLP±Δ so as to produce aresponsive output that indicates a location of defective word orbit-lines in the memory device 1400.

FIG. 15A is a flow chart 1500 that illustrates a test-mode that executesa sense amplifier offset check in accordance with an embodiment. Thetest mode illustrated in FIG. 15 may be executed using, the tester 1402illustrated in FIG. 14. The test-mode generally operates to, rejectdefective dummy write lines and bits lines through sense amplifieroffset checking in an edge reference array 1408 in accordance with thepresent disclosure.

In operation 1502, the tester 1402 executes a test-mode entry of thebit-line merge signal 1460 and the test mode option signal 1448 signalsas described above. Operation 1502 includes determining the optimalnumber word-lines by the gross testing described above in connectionwith FIG. 10-13.

In operation 1504, the tester 1402 activates one word-line 1440 in thestorage array 1404. The tester may activate the word-line withoutactivating the sense amplifiers 1416. Specifically, the tester 1402drives the storage array word decoder 1444 with an input signal thatselects a particular word-line 1440. At the same time, the poweramplifier enable signal 1452 is de-asserted so as to disable the poweramplifier associated with the sense amplifier 1416.

In operation 1508, the tester 1402 changes the voltage level on thereference array 1408 memory cells once the sense-amplifier-deactivatedword-line activation, of operation 1408 is completed. Here, the tester1302 asserts a voltage on the edge equalization signal 1480, where theasserted voltage is within a predetermined range that is centered on thevoltage (VBLP) of sense amplifier 1416. That voltage may be indicatedherein as VBLP±Δ. By asserting the voltage on the edge equalizationsignal 1480, the voltage is provided to the reference array 1480.Providing the voltage to the reference array 1408 produces an outputthat is determined by the amount which the voltage differs from the baselevel of VBLP. For example if Δ=+˜mv the output data may be expected tobe ‘0.’ If Δ=−˜mv the output data may be expected to be ‘1.’

In operation 1512, the tester 1402 exits test-mode on the bit-line mergesignal 1460. Specifically, the tester 1402 de-asserts the test mergesignal 1460 such that voltage is no longer shared between the referencearray 1408 and the storage array 1404.

In operation 1516, the tester 1402 executes a read operation with thesense amplifiers 1416 activated. In one example, the tester 1402executes a read operation with all column addresses activated, such asthrough a Y-scan operation or the like. The tester 1402 then outputs theresult on the normal read out path.

In operation 1520, the tester 1402 checks the DQ burst data. If the DQburst data state differs from an expected amount, the tester 1302 maytrace the defect to a specific cell location. The defective cell maythen be replaced with a redundancy dummy cell. In some embodiments, asimilar test may be done with plate-bump test and so. However, thisproposed test can be avoided based on other factors that vary a signalamount. In operation 1524, the tester 1402 ends the test flow.

FIGS. 16A-B are diagrams for example sense amplifier controllers inaccordance with the present disclosure. FIG. 16A is a circuit diagramfor an example sense amplifier controller 1600 that may be used inconnection with a reference memory array 108 in accordance with thepresent disclosure. FIG. 16B is a circuit diagram for an example senseamplifier controller 1602 that may be used in connection with a storagememory array 104 in accordance with the present disclosure. Both of theexample controllers 1600, 1602 are shown coupled to portions of anexample sense amplifier circuit, which is shown in greater detail inconnection with FIG. 2. The circuit of FIG. 16B illustrates a couplingof various control signals through a gate network 1604 to transistors ofthe sense amplifier circuit 200. The circuit of FIG. 16A illustratessimilar couplings and additional includes couplings for TmBLMerge 1608and TmBLEQ 1612. As shown in FIG. 16A, the TmBLMerge 1608 and TmBLEQ1612 may be coupled to gates of the sense amplifier circuit 200 througha gate network 1616 that includes a delay circuits 1620 coupled to thegates of additional sense amplifier transistors 1624, 1628.

FIGS. 17A-B are diagrams for example LIO-EQ circuits in accordance withthe present disclosure. FIG. 17A is a circuit diagram for an exampleLIO-EQ circuit 1700 for a reference memory array 108 that uses a normaldata output path as shown in FIG. 12. FIG. 17B is a circuit diagram foran example LIO-EQ circuit 1702 for a storage memory array 104 that usesa normal data output path as shown in FIG. 12. Both of the LIO-EQcircuits 1700, 1702 are shown coupled to portions of an example senseamplifier circuit 200, which is shown in greater detail in connectionwith FIG. 2. The circuit of FIG. 17B illustrates a coupling of variouscontrol signals through a gate network 1704 to transistors of the senseamplifier circuit 200. The circuit of FIG. 17A illustrates a gatenetwork 1708 that includes similar couplings and additionally includescouplings for TmBLMerge 1712.

FIGS. 18A-B are diagrams for example RWAMP circuits in accordance withthe present disclosure. FIG. 18A is a circuit diagram for an exampleRWAMP circuits 1800 that ma be used in connection with a referencememory array 108 that provides EQ-level output via edge-RWAMP, such asshown in FIG. 1C or FIG. 10. FIG. 18B is a circuit diagram for exampleRWAMP circuits 1802 that may be used in connection with a referencememory array 108 that provides EQ-level output via a RWAMP associatedwith the normal data output path, such as shown in FIG. 12. Both of theexample RWAMP circuits 1800, 1802 are shown coupled to read/writeamplifiers 1804 used to read and write data across global data lines.The circuit of FIG. 18B illustrates a coupling of various controlsignals through a gate network 1808 to the read/write amplifiers 1804.The diagram of FIG. 18A illustrates a coupling of various controlsignals through a gate network 1812 to the read/write amplifiers 1804,as well as couplings to portions of a sense amplifier 200 (which isillustrated in greater detail in FIG. 2.

The various systems and methods disclosed herein have many advantagesand benefits. A reference array in accordance with the presentdisclosure may reduce the area of an edge section in a memory arraydevice. Reference array embodiments may also improve cell efficiency byusing pseudo-load via a dummy Cell, Mos-cap, and so on. Using dummymemory cells and dummy word-lines as described herein can improve asense amplifier operation margin by balancing complementary bit-lines inan optimal way. Using dummy memory cells in this manner provides forgreater timing control and may involve a negligible area penalty. Thevarious testing procedures described herein provide a manageable testflow that adjusts the edge load to match the real (inner) load of abit-line. The testing procedures also provide an adjustable mechanism toreject defects in word and bit-lines. All these features areadvantageous as future memory devices are designed with longer bit-linelengths and lowered operational voltages.

The above specification, examples and data provide a completedescription of the structure and use of exemplary embodiments of theinvention as defined in the claims. Although various embodiments of theclaimed invention have been described above with a certain degree ofparticularity, or with reference to one or more individual embodiments,those skilled in the art could make numerous alterations to thedisclosed embodiments without departing from the spirit or scope of theclaimed invention. Other embodiments are therefore contemplated. It isintended that all matter contained in the above description and shown inthe accompanying drawings shall be interpreted as illustrative only ofparticular embodiments and not limiting. Changes in detail or structuremay be made without departing from the basic elements of the inventionas defined in the following claims.

The foregoing description has broad application. The discussion of anyembodiment is meant only to be explanatory and is not intended tosuggest that the scope of the disclosure, including the claims, islimited to these examples. In other words, while illustrativeembodiments of the disclosure have been described in detail herein, theinventive concepts may be otherwise variously embodied and employed, andthe appended claims are intended to be construed to include suchvariations, except as limited by the prior art.

1. An apparatus comprising: a first memory cell array comprising a firstbit-line and a plurality of normal word lines coupled to the firstbit-line; a second memory cell array comprising a second bit-line and aplurality of dummy word lines coupled to the second bit-line, the numberof dummy word lines being smaller than that of the normal word lines; asense amplifier coupled to the first bit-line and a first end of thesecond bit-line; a first word decoder configured to activate one of theplurality of normal word lines during a memory access operation to amemory cell coupled to the one of the plurality of normal word lines;and a second word decoder configured to activate two or more of theplurality of dummy word lines during the memory access operation.
 2. Theapparatus of claim 1, wherein the second word decoder is configured tooperate selected ones of the plurality of dummy word lines responsive toa first test signal; and the apparatus further comprises: a transistorcoupled to a second end of the second bit-line and operated by a secondtest signal.
 3. The apparatus of claim 2, further comprising: atransistor edge network including a plurality of bit-line transistorseach coupled to bit-lines in the second memory cell array; wherein thetransistor is coupled to the second end of the second bit-line throughthe transistor edge network.
 4. The apparatus of claim 3, wherein thetransistor edge network receives a merged bit-line output from eachbit-line in the second memory cell array and joins the merged bit-lineoutputs together into a bundled output that is provided to thetransistor.
 5. The apparatus of claim 4, wherein the second test signaladditionally operates to turn off a power supply in the sense amplifierwhich generates the merged bit-line outputs by enabling voltage sharingbetween the bit-lines of the first and second memory cell arrays.
 6. Theapparatus of claim 4, further comprising: a comparator having a firstinput coupled to the transistor and a second input coupled to areference voltage; wherein the comparator is configured to compare thebundled output provided by the transistor to the reference voltage andto provide a responsive output signal at a comparator output.
 7. Theapparatus of claim 6, wherein the responsive output signal includes oneof two possible output states such that the particular output stateprovided by the comparator output at a particular time depends on acomparison of the first and second comparator inputs; and a transitionbetween output states indicates that capacitance on the first and secondbit-lines is substantially balanced.
 8. The apparatus of claim 6,wherein the comparator output is used in a test mode that is executed todetermine the activated two or more of the plurality of dummy word linefor the second memory cell array.
 9. The apparatus of claim 1, whereinthe second memory cell array is a reference array arranged at an edge ofthe apparatus.
 10. The apparatus of claim 1, wherein the second memorycell array is a reference array arranged between memory banks associatedwith the apparatus.
 11. An apparatus comprising: a normal memory cellarray comprising a first bit-line and a plurality of normal word linescoupled to the first bit-line; a reference memory cell array comprisinga second bit-line and a plurality of dummy word lines coupled to thesecond bit-line, the number of dummy word lines being smaller than thatof the normal word lines and arranged at an edge of the apparatus; asense amplifier coupled to the first bit-line and a first end of thesecond bit-line; a first word decoder configured to activate one of theplurality of normal word lines during a memory access operation to amemory cell coupled to the one of the plurality of normal word lines;and a second word decoder configured to activate two or more of theplurality of dummy word lines during the memory access operation,wherein the sense amplifier senses information on the first and secondbit lines responsive to the one of the plurality of normal word linesand the two or more of the plurality of dummy word lines beingactivated.
 12. The apparatus of claim 11, wherein the second worddecoder is configured to operate selected ones of the plurality of dummyword lines responsive to a first test signal; and the apparatus furthercomprises: a transistor coupled to a second end of the second bit-lineand operated by a second test signal.
 13. The apparatus of claim 12,further comprising: a transistor edge network including a plurality ofbit-line transistors each coupled to bit-lines in the second memory cellarray; wherein the transistor is coupled to the second end of the secondbit-line through the transistor edge network.
 14. The apparatus of claim13, wherein the transistor edge network receives a merged bit-lineoutput from each bit-line in the reference memory cell array and joinsthe merged bit-line outputs together into a bundled output that isprovided to the transistor.
 15. The apparatus of claim 14, wherein thesecond test signal additionally operates to turn off a power supply inthe sense amplifier which generates the merged bit-line outputs byenabling voltage sharing between the bit-lines of the normal andreference memory cell arrays.
 16. The apparatus of claim 14, furthercomprising: a comparator having a first input coupled to the transistorand a second input coupled to a reference voltage; wherein thecomparator is configured to compare the bundled output provided by thetransistor to the reference voltage and to provide a responsive outputsignal at a comparator output.
 17. The apparatus of claim 16, whereinthe responsive output signal includes one of two possible output statessuch that the particular output state provided by the comparator outputat a particular time depends on a comparison of the first and secondcomparator inputs; and a transition between output states indicates thatcapacitance on the first and second bit-lines is substantially balanced.18. The apparatus of claim 16, wherein the comparator output is used ina test mode that is executed to determine the activated two or more ofthe plurality of dummy word line for the reference memory cell array.